This invention relates generally to the emission of electrons and more particularly to an improved microchannel plate type of electron amplifier.
Various electronic devices involve the generation of electrons within a vacuum chamber, such electrons being liberated as emissions from a solid surface of an electrode. An electron emission system wherein the pulse modulating characteristics of impinging light entering a vacuum chamber from a laser source to supply the requisite emission triggering energy, is disclosed for example in U.S. Pat. No. 4,313,072 to Wilson et al.
Electron emission devices including microchannel plates are also generally known in the art as disclosed for example in U.S. Pat. Nos. 4,147,932 and 4,701,618 to Lewis and Tosswill. Such microchannel plates consist of an array of small cylinder shaped, continuous dynode electron multipliers through which current amplification is achieved by secondary electron emissions. The secondary emission phenomenon involves the bombardment of solid electron emitting surfaces with electrons.
Standard microchannel plates acting as an electron amplifier are desirable because of certain associated characteristics such as high gain, low noise, etc. However, because of other accompanying characteristics electron current density is severely limited by plate overheating. Such microchannel plates furthermore require plate bias current at least 10 times the output current at gain saturation exhibiting at most 10% efficiency. Accordingly, operation of microchannel plate devices at higher current levels was not deemed to be desirable.
It is therefore an important object of the present invention to provide a modified form of microchannel plate acting as an electron amplifier which is capable of being pulse modulated at high repetition rates and short pulse widths and yet produce moderate current density without overheating while retaining other desirable characteristics of standard microchannel plates.
Further objects of the invention in accordance with the foregoing object is to provide a microchannel type of electron emission source that is more efficient, in both a linear and saturated mode, and capable of isolating pulse modulating signal inputs from high post-acceleration voltages in a wide range of applications.